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Message-ID: <20240523084327.2013211-1-geomatsi@gmail.com>
Date: Thu, 23 May 2024 11:43:23 +0300
From: Sergey Matyukevich <geomatsi@...il.com>
To: linux-riscv@...ts.infradead.org,
linux-kernel@...r.kernel.org
Cc: Anup Patel <anup@...infault.org>,
Atish Patra <atishp@...osinc.com>,
Palmer Dabbelt <palmer@...belt.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Albert Ou <aou@...s.berkeley.edu>,
Samuel Holland <samuel.holland@...ive.com>,
Alexandre Ghiti <alexghiti@...osinc.com>,
Conor Dooley <conor.dooley@...rochip.com>,
Sergey Matyukevich <sergey.matyukevich@...tacore.com>
Subject: [PATCH v2] riscv: prevent pt_regs corruption for secondary idle threads
From: Sergey Matyukevich <sergey.matyukevich@...tacore.com>
Top of the kernel thread stack should be reserved for pt_regs. However
this is not the case for the idle threads of the secondary boot harts.
Their stacks overlap with their pt_regs, so both may get corrupted.
Similar issue has been fixed for the primary hart, see c7cdd96eca28
("riscv: prevent stack corruption by reserving task_pt_regs(p) early").
However that fix was not propagated to the secondary harts. The problem
has been noticed in some CPU hotplug tests with V enabled. The function
smp_callin stored several registers on stack, corrupting top of pt_regs
structure including status field. As a result, kernel attempted to save
or restore inexistent V context.
Fixes: 9a2451f18663 ("RISC-V: Avoid using per cpu array for ordered booting")
Fixes: 2875fe056156 ("RISC-V: Add cpu_ops and modify default booting method")
Signed-off-by: Sergey Matyukevich <sergey.matyukevich@...tacore.com>
Reviewed-by: Alexandre Ghiti <alexghiti@...osinc.com>
---
Changes since v1 [1]:
- fixed git revisions in commit message
[1] https://lore.kernel.org/linux-riscv/20240424221927.900612-1-geomatsi@gmail.com/
---
arch/riscv/kernel/cpu_ops_sbi.c | 2 +-
arch/riscv/kernel/cpu_ops_spinwait.c | 3 +--
2 files changed, 2 insertions(+), 3 deletions(-)
diff --git a/arch/riscv/kernel/cpu_ops_sbi.c b/arch/riscv/kernel/cpu_ops_sbi.c
index 1cc7df740edd..e6fbaaf54956 100644
--- a/arch/riscv/kernel/cpu_ops_sbi.c
+++ b/arch/riscv/kernel/cpu_ops_sbi.c
@@ -72,7 +72,7 @@ static int sbi_cpu_start(unsigned int cpuid, struct task_struct *tidle)
/* Make sure tidle is updated */
smp_mb();
bdata->task_ptr = tidle;
- bdata->stack_ptr = task_stack_page(tidle) + THREAD_SIZE;
+ bdata->stack_ptr = task_pt_regs(tidle);
/* Make sure boot data is updated */
smp_mb();
hsm_data = __pa(bdata);
diff --git a/arch/riscv/kernel/cpu_ops_spinwait.c b/arch/riscv/kernel/cpu_ops_spinwait.c
index 613872b0a21a..24869eb88908 100644
--- a/arch/riscv/kernel/cpu_ops_spinwait.c
+++ b/arch/riscv/kernel/cpu_ops_spinwait.c
@@ -34,8 +34,7 @@ static void cpu_update_secondary_bootdata(unsigned int cpuid,
/* Make sure tidle is updated */
smp_mb();
- WRITE_ONCE(__cpu_spinwait_stack_pointer[hartid],
- task_stack_page(tidle) + THREAD_SIZE);
+ WRITE_ONCE(__cpu_spinwait_stack_pointer[hartid], task_pt_regs(tidle));
WRITE_ONCE(__cpu_spinwait_task_pointer[hartid], tidle);
}
--
2.44.0
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